Thanks cafeIke. That graph and link helped a lot. I am still trying to perfect my shots (still bitter) but I still have A LOT to learn. Feel free to come by and give me some lessons.

Hey guys, I just want to thank you for posting this thread! I have been trying to find out how the temp changes from the puck to the cup at coffeegeek but nobody would provide me the answer. This makes me think that I underestimated the change in temperature and may be burning my coffee, thus giving me the bitter taste despite having too short a shot time. My machine is too low on its own, but with proper prep I have been reaching and then exceeding my goal. I was imagining more along the lines of a 10 degree change, but 30 puts me way over where I want to be at the puck. At any rate, I can do much more accurate experimenting with this data! Excellent.